Can I Replace ICL7660 With TC1044SCPA?

[Brad Hill]

I'm working on a project with a charge pump and have run into the dreaded oscillation/whine of the ICL7660.  I have used both the "C" and "S" variants without any luck in removing the noise.

I happen to have a few TC1044SCPA's in my collection and see that a fellow on another forum used one successfully in his build so I am curious to know if anyone confirm that the TC1044SCPA is an acceptable alternative for the ICL7660S (the spec's appear to be similar but I am quite new to reading those things!)?

Any help would be MUCH appreciated!


- brad -

[m-Kresol]

yes, you should be able to interchange them.
One more thing, for audio use you'll always need the S version, which has the "booster" pin (1 or 8, not sure atm) which shifts the switching frequency out of the audible range.

how do you power your build? could also be the combination of pedal with PSU, if that one is a switching psu. Also, are there any other builds in the chain with a charge pump? this can lead to heterodyning as well.

good luck

[Brad Hill]

Thanks for the quick reply.

In my mind I was ordering the "s" version of the ICL7660 from Tayda and didn't realize I actually pulled the trigger on the TC1044SCPA until it arrived (yet another one of my many brain cramp moments!).

This is going into the Tayda Plexitone kit (similar to the Boneyard if I'm not mistaken) which has some known oscillation issues.

I power my pedal collection with a Godlyke "power-all" and I don't have any other charge pumps before or after this one.

I have minimized the whine/whistle by changing the orientation of a few wires inside the build and have tried some cheap eBay ICL7660S ICs but I don't have 100% confidence in those.  Hopefully the TC1044SCPA might elliminate the issue altogether!

- brad -

[m-Kresol]

i see. the 7660 and 1044 are pretty similar I think. at least from my non-professional point of view.
if your problems persist and you say it is affected by wire positioning, I'd strongly suggest to use shielded wire for in and output.

[neandrewthal]

I got some 7660s from Tayda. Never again. The tinfoil hat on the output jack(which is literally touching the charge pump) in this project cured 60% of the problem but I got a bunch of cheap LT1054s from Aliexpress and never looked back...except now....and when I posted that picture. 

http://www.madbeanpedals.com/forum/index.php?topic=23725.0

If you want results now (Things from Ali express take forever) and have a chip better than the 7660 I would just try popping it in and see what happens.

[m-Kresol]

LT1054 are usually not exchangeable with 7660. They don't have the booster pad as the lt1054 already has a high switching frequency. Tying pin 1&8 together will do you no good with the 1054.